2.2.6.3 Reducing Headlight Reflection and GlareSince porous asphalt acts as a drainage layer, rainwater is able to seep through the mix , reflection and glare from vehicle headlights are reduced and thus visibility Road markings painted on the wet surface at night can be improved (Manfred N. Partl, 2006). Despite this, the driver's visibility at night can be increased by reducing glare.2.2.6.4 Noise reductionA high air void content and the maximum stone size of the porous asphalt surface are vital to the degree of sound absorption while smaller aggregate sizes tend to produce less noise ( Studente, 2005 ). Furthermore, the noise produced between the surface and the vehicle tire can be absorbed by the coarse macrostructure of the porous asphalt surface (Manfred N. Partl, 2006).2.2.7 Disadvantages of porous asphaltUnfortunately, although porous asphalt has many advantages but there are also some disadvantages for road safety and environment.2.2.7.1 Aging and strippingAccording to Ali et al. (2012), porous asphalt pavement ages much faster than regular asphalt due to high porosity. Additionally, rainwater can diffuse into the porous matrix and make the asphalt wet as the water remains in the pavement structure. Therefore, the binding film may move from the surface of the aggregates due to moisture damage. 2.2.7.2 Clogging Loss of permeability due to clogging is another factor that affects the performance of porous asphalt pavement. The advantages of noise reduction and draining function will gradually disappear when the pores affected by the obstruction are lost (Manfred N. Partl, 2006). The pores of porous asphalt can be blocked by dirt, dust or other...... half of the paper ...... crushed hard rock, angular in shape and free of dust, clay and other material substances must be screened (PWD Malaysia, 2008). Referring to PWD Malaysia Standard Specification for Road Works (2008), coarse aggregates should have abrasion and impact loss in Los Angeles machine not exceeding 25% when tested in accordance with ASTM C 131 Since porous asphalt It is mainly used as a wear layer, it is essential that the aggregate resists polishing. The value of polished stone when tested in accordance with MS 30 shall not be less than 40 (PWD Malaysia, 2008). As indicated above, the fine aggregates recommended to be used should be screened quarry fines only. According to the standard specifications of PWD Malaysia (2008), fine aggregates must be non-plastic and free from clay, loam, aggregates, vegetative substances and other deleterious substances.